Not so long ago I found a “Line Width” attribute under “Extra Attributes” in my Maya’s Shape nodes, for curves.

I got excited, as it allows me to set individual thickness to any control in rigs, making them easier to spot, and most importantly - select, as this thickness influences selection pixels as well. Unfortunately I could not confirm for myself whether it was a standard feature in Maya or if it’s added by one of the plugins I have installed.

I know that there’s one for global line thickness in Preferences, it’s not the one I’m talking about. This one I’m talking about can be found after selecting Shape node and going to Attribute Editor, Extra Attributes - Line Width.

So questions are:

Is this a built-in\default feature in Maya?

If it is, when was it first implemented?

Is there any information about it in documentation that I could not find?

Yes, it is a standard feature of Maya, and has been there for as long as I can remember (which doesn’t really help answer your second question…).
Also, I couldn’t find any documentation about it either I think it’s so ubiquitous that there may not be a need for it…?

It’s just really odd that a standard attribute is hidden under “Extra Attributes” dropdown. I don’t think I ever saw anything like that in other nodes. And I think that you can actually find literally any other parameter in help files.

That’s an interesting feature, I hadn’t seen it before either. Are you sure it influences selection space? In my quick test it doesn’t seem to widen the selectable area. I can click directly on the thick curve, and it doesn’t get selected. Am I missing something?

Edit: Just did some sleuthing, and it seems to be new in 2016. If you look at the node reference, you can see the lineWidth attribute on the nurbsCurve page. 2015 doesn’t have it.